NK、Treg和Th17细胞及其相关免疫分子在羊种布氏菌感染导致模型小鼠流产中的作用

Brucellosis is a widespread and economically important zoonosis caused by bacteria of the genus Brucella. Inner Mongolia is the most serious area sufferring from Brucellosis in China,and Brucella melitensis has been confirmed to be the most important agent. Brucella spp. are Gram-negative, facultative intracellular pathogens that cause abortion in numerous domestic and wild mammals. As results, the abortion may end in a great financial loss and increase the risk of infection in animals and population from various modes of transmission. The immunologic interaction between the fetus and the mother is a paradoxical communication that the fetus is thought to be protected from the maternal immune system, which is defined as the maternal-fetal immune tolerance. The tolerance plays a key role in pregnancy and gestation. The break of the immune tolerance may lead to pregnancy and gestation disorders including unexplained recurrent spontaneous abortion(URSA) and premature delivery. Although the precise cellular and molecular mechanisms underlying the maintenance of the maternal-fetal immune tolerance and the induction of abortion remain unclear, the immune cells NK, Treg, Th17 and relevant immune molecules are proved to play important roles. The immune mechanism of destroying the maternal-fetal immune tolerance due to the Brucella infection needs further study. The project is designed to discuss the immune mechanism in the abortion model of pregnant mice induced by B.melitensis infection, in which the abortus models of mice would be constructed and a series of immunological indicators (NK cell, Treg, Th17 and relevant immune molecules in the peripheral blood and placenta )may be detected and compared with the spontaneous abortus models ( the control group) . These results may deepen the understanding of the cellular and molecular mechanism in abortion due to the Brucella infection and progress the research of Brucellosis.

布鲁氏菌病（简称布病）是由布氏菌感染引起的一种自然疫原性人畜共患传染病，主要由动物传播给易感人群。内蒙古地区布病发病率连年位居全国之首，羊种是主要流行株。布氏菌是兼性细胞内寄生菌（主要寄生于巨噬细胞和胚胎滋养层细胞），感染牲畜后可引起流产、死胎、公畜不育，可多途径感染易感人群。母-胎间免疫耐受的建立和维持是保证正常妊娠的基础，一旦免疫耐受被破坏，可发生流产、早产等。免疫细胞特别是NK、Treg和Th17细胞及其之间动态平衡在建立和维持母-胎免疫耐受中发挥重要作用。布氏菌感染孕畜后如何破坏母-胎间免疫耐受导致流产的免疫学作用机制尚不十分清楚。本项目拟利用羊种布氏菌感染诱发孕鼠流产模型，以正常妊娠和自然流产模型为对照组，通过对外周血和胎盘中NK、Treg和Th17及其相关免疫分子检测，探讨上述细胞及分子在布氏菌感染所致孕期动物流产中的作用及作用机制，为布病致病机制研究及早期预防提供实验基础。

布鲁氏菌病是由布氏菌感染引起的一种人畜共患传染病。布氏菌为兼性细胞内寄生菌，感染牲畜后易引起母畜流产、死胎等，造成畜牧养殖业重大损失并增加人群感染的几率。母-肽间免疫耐受的建立和维持是保证正常妊娠的基础，这种耐受一旦被破坏，可发生流产、早产等。为了探讨布氏菌感染孕畜后如何打破母-胎间免疫耐受并导致流产的作用机制，本项目利用羊种布氏菌M5株感染不同孕期孕鼠建立了动物流产模型，以正常妊娠小鼠为对照组，对各组小鼠流产率、胎盘中NK、Treg和Th17及其免疫分子等进行检测。结果表明，羊种布氏菌M5菌株以1×106CFU/只剂量经皮下注射孕10d的CBA/J小鼠可建立稳定的布氏菌感染导致孕鼠流产模型；与正常妊娠组相比，感染模型小鼠的外周血和胎盘蜕膜组织中Treg细胞比例降低而Th17和NK1.1细胞比例均升高；胎盘滋养层细胞培养上清中IFN-γ和IL-17A显著升高，IL-6则明显降低。通过尾静脉回输正常小鼠来源的Treg可以降低胎盘吸收率，而回输Th17细胞后小鼠胎盘吸收率则明显升高。我们的研究结果提示，胎盘蜕膜局部Treg和Th17之间的动态平衡以及NK细胞比例失衡是羊种布氏菌感染导致孕鼠流产的重要原因，IFN-γ和IL-17A等炎性细胞因子表达升高可能进一步促进流产的发生。